1. Field of the Invention
The present invention relates generally to vascular catheters, and in particular to improved vascular catheters and methods for their insertion into the vascular anatomy over guide wires.
Atherosclerosis is a common human ailment arising from deposition of fatty-like substances, referred to as atheroma or plaque, on the walls of blood vessels. Such deposits occur both in the peripheral blood vessels, which feed the limbs of the body, and the coronary vessels, which feed the heart. When deposits accumulate in localized regions of a blood vessel, narrowing of the vascular lumen, referred to as stenosis occurs. Blood flow is restricted and the person's health is at serious risk.
Numerous approaches for opening such stenosed regions are known. Of particular interest to the present invention are approaches which introduce diagnostic or therapeutic devices into the vascular anatomy through a catheter or a sheath. For instance, one known approach is balloon angioplasty where a balloon-tipped catheter is used to dilate a stenosed region (optionally in combination with a stent for maintaining patency). In another approach referred to as atherectomy, a blade, cutting element or other abrasive element, is introduced through a catheter or sheath and is used to remove the atheroma or plaque. Other approaches include spark gap reduction where an electric spark burns through the atheroma or plaque, and laser angioplasty where laser energy is used to ablate at least a portion of the atheroma or plaque. With any one of these approaches, it is often desirable to obtain an image of the interior of the blood vessel at the region to be treated. Catheters having imaging elements such as ultrasonic transducers are now gaining widespread acceptance for producing such images.
Ultrasonic imaging catheters will often include an imaging core comprising ultrasonic imaging transducer or reflective element mounted on a rotatable drive shaft disposed within a flexible catheter body. The transducer, reflective element or both, can be rotated within the catheter body to direct an ultrasonic signal generally outward in order to scan the interior of the blood vessel wall. High resolution images revealing information concerning the extent and nature of the stenotic material can thus be produced.
During diagnostic, imaging, and interventional vascular procedures, it is often desirable to "exchange" one catheter for another. By "exchange" it is meant that one catheter is withdrawn from the vascular system and another catheter is introduced to the vascular system. In order to maintain distal access, the exchange will usually be performed over a guide wire which is left in place to facilitate both catheter withdrawal and reintroduction of the new catheter.
Of particular interest to the present invention are "rapid exchange" catheter designs. Unlike earlier catheter designs (referred to hereinafter as "conventional over-the-wire" designs) where the entire catheter body was inserted over the guide wire, the rapid exchange catheters have a guide wire lumen that does not extend the full length of the catheter. Rather, the guide wire lumen extends only from the distal tip to a side "exit" port which terminates a short distance proximal of the distal tip. Two rapid exchange catheter designs which are of particular interest to the present invention are long lumen rapid exchange designs and short lumen rapid exchange designs (the latter sometimes being referred to as "monorail" designs).
In the case of long lumen rapid exchange catheters, the side port through which the guide wire exits will typically be 10 cm or more from the distal tip of the catheter. In a particular type of long lumen rapid exchange catheters, referred to as a common lumen rapid exchange catheter or sheath, the catheter body includes a working lumen in addition to the guide wire lumen. These two lumens are disposed in a proximal region of the catheter and are in communication with a common lumen at a distal region of the catheter. The guide wire is introduced through the common lumen and advanced into the proximal guide wire lumen when inserting the catheter into a patient. The relatively long engagement of the guide wire with common lumen and the guide wire lumen allows the distal end of the catheter to more easily be passed through tortuous regions of the vascular anatomy. This is often referred to as providing the catheter with good "trackability".
Another advantage of common long lumen rapid exchange catheters is that once the catheter is in the desired region of the vascular anatomy, the guide wire can be withdrawn from the vessel, and stored in the guide wire lumen just proximal to the common lumen. A diagnostic or therapeutic device can then be advanced from the working lumen and into the common lumen without being obstructed by the guide wire. This is especially desirable when an imaging core is advanced into the common lumen so that imaging can occur without obstruction from the guide wire.
A further advantage of common long lumen rapid exchange designs is that the common lumen of the catheter serves as a protector for the imaging core. This is of particular importance when imaging an area of a vessel displaced by a stent. The common lumen of the catheter or sheath protects the imaging core from unexpected collapse of the stent.
Common long lumen rapid exchange catheters are also advantageous in that the guide wire can easily be readvanced from the stored location in the guide wire lumen, through the common lumen, and into the vessel. Once the guide wire is readvanced into the vessel, the catheter can be repositioned or removed while the guide wire protects the vessel. In still another advantage, the long engagement with the guide wire prevents buckling and prolapse of the guide wire when removing the catheter from the vessel.
Drawbacks to common long lumen rapid exchange designs include the possibility of damaging the artery with the distal tip of the catheter when the guide wire is removed from the distal region and stored in the guide wire lumen. Without the guide wire to secure the catheter in the vessel, the distal tip of the catheter can accidently be advanced causing damage to the artery. Another problem experienced with long lumen rapid exchange catheters is that, in emergency situations, some physicians will withdraw the entire catheter from the patient (along with the guide wire), instead of readvancing the guide wire from the guide wire lumen and into the vessel, and then removing the catheter with the guide wire still in place.
Short lumen rapid exchange catheter designs generally employ a much shorter guide wire lumen at the distal end of the catheter, typically in the range from about 1 cm to 4 cm. Further, unlike the long lumen rapid exchange catheters, the guide wire lumen is not disposed within the proximal region of the catheter body. Hence, the guide wire is usually not removed from the vessel when using short lumen rapid exchange designs.
Once the short lumen rapid exchange catheter is positioned in the artery, an interventional, imaging, or diagnostic component of a catheter may then be disposed proximally through a separate access lumen in the short lumen rapid exchange catheter body and up to the guide wire lumen. Alternatively, a fixed interventional element such as an angioplasty balloon may be disposed on the catheter body proximal to the short guide wire lumen. Since a majority of the length of the guide wire is not stored in the catheter body, the cross sectional area of the catheter can be made smaller than most long lumen rapid exchange designs while still providing space for introducing other devices. As previously described, the short lumen rapid exchange design also allows the guide wire to remain in place in the vessel. This allows for easy removal of the catheter and the insertion of another catheter along the guide wire.
While such short lumen rapid exchange designs have proven to be very valuable, particularly for introduction of catheters to very small blood vessels, the small engagement of the guide wire with the catheter has proven problematic. For instance, short lumen rapid exchange designs have poor trackability. Further, buckling or prolapse of the guide wire can occur when removing the catheter from the vessel.
For these reasons, two or more different catheters can be introduced during a single operation. This can be inconvenient to a surgeon who may be required to remove a variety of different catheters from their packages and then introduce these into the patient. Furthermore, the use of several different catheter designs can increase the cost of the operation.
It would thus be desirable to provide catheters and sheaths incorporating features of both a long lumen rapid exchange design and a short lumen rapid exchange design for use in vascular procedures. For instance, it would be desirable to employ the long lumen rapid exchange design in situations where trackability is required and the short lumen rapid exchange catheter to treat very small vessels.
2. Description of the Background Art
Vascular ultrasonic imaging catheters having rapid exchange designs are described in U.S. Pat. Nos. 5,201,316; 5,024,234; and 4,951,677. Catheter sheaths having guide wire side ports near their distal ends are described in U.S. Pat. Nos. 4,932,413; 4,824,435; and 4,552,554. A short lumen rapid exchange balloon dilation catheter is described in U.S. Pat. No. B 1 4,762,129. An ultrasonic imaging catheter having a common distal lumen is described in U.S. Pat. No. 5,203,338. A monorail sheath catheter usable with an ultrasonic imaging core was described in a Product Development Update of Intertherapy, Costa Mesa, Cal, dated: Fall 1990. A catheter having a guide wire lumen with a slidable sleeve is described in PCT International Application No. PCT/US93/07323.